U.S. patent application number 12/653122 was filed with the patent office on 2010-06-17 for occupant detection system and method of controlling the system.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Hajime Nakagawa, Shoichi Yamanaka.
Application Number | 20100152975 12/653122 |
Document ID | / |
Family ID | 42241541 |
Filed Date | 2010-06-17 |
United States Patent
Application |
20100152975 |
Kind Code |
A1 |
Nakagawa; Hajime ; et
al. |
June 17, 2010 |
Occupant detection system and method of controlling the system
Abstract
A capacitance sensor outputs a signal indicating one of an
occupant-seated state, a CRS-mounted state and a vacancy state. A
load sensor is ON when a predetermined load applied to the load
sensor through the seat, and is OFF when the predetermined load is
not applied. A controller turns off both of an on-light indicating
airbag inflation allowance and an off-light indicating airbag
inflation prohibition, when the signal indicates the vacancy state,
and when the load sensor is OFF. The controller turns on the
off-light, when the signal indicates the vacancy state, and when
the load sensor is ON.
Inventors: |
Nakagawa; Hajime;
(Nagoya-city, JP) ; Yamanaka; Shoichi; (Anjo-city,
JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO CORPORATION
Kariya-city
JP
|
Family ID: |
42241541 |
Appl. No.: |
12/653122 |
Filed: |
December 8, 2009 |
Current U.S.
Class: |
701/45 ;
324/686 |
Current CPC
Class: |
B60R 21/01532 20141001;
B60R 21/01516 20141001; B60R 21/01522 20141001 |
Class at
Publication: |
701/45 ;
324/686 |
International
Class: |
B60R 21/015 20060101
B60R021/015; G01R 27/26 20060101 G01R027/26 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 11, 2008 |
JP |
2008-316109 |
Oct 26, 2009 |
JP |
2009-245754 |
Claims
1. An occupant detection system comprising: a capacitance sensor to
output a current/voltage signal based on a variation of weak
electric field generated between a ground and an electrode arranged
in a seat, the signal being one of an occupant-seated signal
indicating an occupant seated on the seat, a CRS-mounted signal
indicating a child restraint system mounted on the seat, and a
vacancy signal indicating the seat being vacant; a load sensor
arranged in the seat, the load sensor being ON when a
predetermined, load is applied to the load sensor through the seat,
the load sensor being OFF when the predetermined load is not
applied; and a controller to control an on-light indicating airbag
inflation allowance for the seat, and an off-light indicating
airbag inflation prohibition for the seat, wherein the controller
turns on the on-light, when the occupant-seated signal is output,
and when the load sensor is ON or OFF, the controller turns on the
off-light, when the CRS-mounted signal is output, and when the load
sensor is ON or OFF, the controller turns on the off-light, when
the vacancy signal is output, and when the load sensor is ON, and
the controller turns off both of the on-light and the off-light,
when the vacancy signal is output, and when the load sensor is
OFF.
2. The occupant detection system according to claim 1, wherein the
load sensor includes a pair of films, and a pair of sensor
electrodes arranged between the pair of films, wherein the pair of
sensor electrodes oppose to each other to be distanced from each
other, and the pair of sensor electrodes are configured to be
contact with each other, when a load is applied to the load
sensor.
3. The occupant detection system according to claim 1, wherein the
load sensor has a switch to determine the predetermined load to be
applied or not, and the switch is arranged to be located in a
contact area between the seat and the child restraint system, when
the child restraint system is mounted on the seat.
4. The occupant detection system according to claim 1, wherein the
load sensor has a plurality of switches to determine the
predetermined load to be applied or not, the child restraint system
is one of a plurality of child restraint systems, such that a
plurality of contact areas are defined between the seat and the
child restraint system to correspond to the plurality of child
restraint systems, and the plurality of switches is arranged in a
manner that at least one of the plurality of switches is located in
the contact area relative to all of the plurality of child
restraint systems.
5. The occupant detection system according to claim 1, further
comprising: an urethane pad having a first face and a second face
opposite from each other, wherein the capacitance sensor is
arranged on the first face of the urethane pad, the load sensor is
arranged on the second face of the urethane pad, and the urethane
pad integrates the capacitance sensor and the load sensor.
6. The occupant detection system according to claim 1, further
comprising: an urethane pad having a first face and a second face
opposite from each other; and a connector connected to the
capacitance-sensor and the load sensor, wherein the capacitance
sensor is arranged on the first face of the urethane pad, the load
sensor is arranged on the second face of the urethane pad, and the
urethane pad integrates the capacitance sensor and the load
sensor.
7. A method of controlling an occupant detection system comprising:
controlling a capacitance sensor to output a first signal
indicating one of an occupant-seated state in which an occupant is
seated on a seat, a CRS-mounted state in which a child restraint
system, is mounted on the seat, and a vacancy state in which the
seat is vacant; controlling a load sensor to output a second signal
indicating one of a load-on-state in which a predetermined load is
applied to the load sensor through the seat, and a load-off-state
in which the predetermined load is not applied to the load sensor;
and controlling an ON-light indicating airbag inflation allowance
for the seat, and an OFF-light indicating airbag inflation
prohibition for the seat, based on the first signal and the second
signal.
8. The controlling method according to claim 7, further comprising:
determining the seat to be in the vacancy state, when the first
signal indicates the vacancy state, and when the second signal
indicates the load-off-state, and determining the seat to be in the
CRS-mounted state, when the first signal indicates the vacancy
state, and when the second signal indicates the load-on-state.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application No.
2008-316109 filed on Dec. 11, 2008 and Japanese Patent Application
No. 2009-245754 filed on Oct. 26, 2009, the disclosures of which
are incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an occupant detection
system and a method of controlling the occupant detection
system.
[0004] 2. Description of Related Art
[0005] JP-A-11-271463 discloses an occupant detection system having
a mat-shaped electrostatic sensor and an electronic control unit
(ECU). When a weak electric field is generated between a vehicle
chassis and a main electrode disposed in an occupant seat, the
electrostatic sensor outputs a variation of the electric field as
current or voltage.
[0006] The electrostatic sensor has a pair of electrodes. When the
occupant seat is vacant, air is filled between the pair of
electrodes. When a child restraint system (CRS) is mounted on the
occupant seat, the CRS is located between the pair of electrodes.
When an occupant is seated on the occupant seat, the occupant is
located between the pair of electrodes.
[0007] Air has a relative permittivity of about 1. The CRS has a
relative permittivity of about 2-5. A body of the occupant has a
relative permittivity of about 50. Thus, the relative permittivity
is different among air, the CRS and the occupant body. Therefore, a
capacitance between the pair of electrodes of the electrostatic
sensor is changed, when a situation of the occupant seat is
changed.
[0008] The variation of the electric field can be output by the
change of the capacitance as current or voltage. The ECU performs a
determination relative to the situation based on the output
current/voltage value. That is, the ECU determines the situation of
the occupant seat to be in a vacancy state, CRS-mounted state or
occupant-seated state.
[0009] Further, an airbag electronic control unit determines an
airbag inflation to be allowable or not based on the situation
determination. Specifically, when the occupant seat is vacant, or
when the CRS is mounted on the occupant seat, the airbag inflation
is prohibited. When the occupant is seated on the occupant seat,
the airbag inflation is allowable.
[0010] When the airbag inflation is allowable, an airbag ON-light
is on to indicate the allowable state. When the airbag inflation is
prohibited, an airbag OFF-light is on to indicate the prohibited
state.
[0011] When the occupant seat is vacant, both of the ON-light and
the OFF-light may be required to be off, because nothing exists on
the occupant seat.
[0012] However, the capacitance of the vacancy state is close to
that of the CRS-mounted state. Even when a one-year-old child, for
example, is seated on the CRS, the capacitance is close between the
CRS-mounted state and the vacancy state. Therefore, it is difficult
to distinguish the situation of the occupant seat to be in the
vacancy state or the CRS-mounted state.
SUMMARY OF THE INVENTION
[0013] In view of the foregoing and other problems, it is an object
of the present invention to provide an occupant detection system
and a method of controlling the occupant detection system.
[0014] According to a first example of the present application, an
occupant detection system includes a capacitance sensor, a load
sensor, and a controller. The capacitance sensor has an electrode
arranged in a seat, so as to output one of an occupant-seated
signal indicating an occupant seated on the seat, a CRS-mounted
signal indicating a child restraint system mounted on the seat, and
a vacancy signal indicating the seat being vacant, based on a
variation of weak electric field generated between the electrode
and a vehicle ground. The load sensor is arranged in the seat. The
load sensor is in an on-state when a predetermined load is applied
to the load sensor through the seat. The load sensor is in an
off-state, when the predetermined load is not applied to the load
sensor. The controller controls an on-light indicating airbag
inflation allowance for the seat, and an off-light indicating
airbag inflation prohibition for the seat. The signals are output
as current or voltage. The controller turns on the on-light, when
the capacitance sensor outputs the occupant-seated signal, and when
the load sensor is in the on-state or the off-state. The controller
turns on the off-light, when the capacitance sensor outputs the
CRS-mounted signal, and when the load sensor is in the on-state or
the off-state. The controller turns on the off-light, when the
capacitance sensor outputs the vacancy signal, and when the load
sensor is in the on-state. The controller turns off both of the
on-light and the off-light, when the capacitance sensor outputs the
vacancy signal, and when the load sensor is in the off-state.
[0015] Accordingly, a situation of the seat can be accurately
determined.
[0016] According to a second example of the present application, a
method of controlling an occupant detection system includes a
controlling of a capacitance sensor to output a first signal
indicating one of an occupant-seated state in which an occupant is
seated on a seat, a CRS-mounted state in which a child restraint
system is mounted on the seat, and a vacancy state in which the
seat is vacant. Further, the controlling method includes a
controlling of a load sensor to output a second signal indicating
one of an on-state in which a predetermined load is applied to the
load sensor through the seat, and an off-state in which the
predetermined load is not applied to the load sensor. Furthermore,
the controlling method includes a controlling of an ON-light
indicating airbag inflation allowance for the seat, and an
OFF-light indicating airbag inflation prohibition for the seat,
based on the first signal and the second signal.
[0017] Accordingly, the vacancy state and the CRS-mounted state can
be accurately distinguished from each other.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0019] FIG. 1 is a block diagram illustrating an occupant detection
system according to an embodiment;
[0020] FIG. 2 is schematic view illustrating a capacitance sensor
of the occupant detection system;
[0021] FIG. 3 is a schematic equivalent circuit diagram
illustrating an object to be detected by the occupant detection
system;
[0022] FIG. 4 is a schematic view illustrating an impedance of the
object;
[0023] FIG. 5A is a signal waveform applied to the object, FIG. 5B
is a signal waveform for sampling a real part of the impedance,
FIG. 5C is a signal waveform for sampling an imaginary part of the
impedance, FIG. 5D is an output signal of the real part, and FIG.
5E is an output signal of the imaginary part;
[0024] FIG. 6 is a diagram illustrating determination logic of the
occupant detection system;
[0025] FIG. 7 is a schematic diagram illustrating a load sensor of
the occupant detection system;
[0026] FIG. 8 is a schematic plan view illustrating another load
sensor of the occupant detection system;
[0027] FIG. 9 is an enlarged cross-sectional view illustrating the
another load sensor;
[0028] FIG. 10 is a front view illustrating an occupant seat having
the another load sensor;
[0029] FIG. 11A is a first example circuit diagram illustrating the
another load sensor, and FIG. 11B is a second example circuit
diagram illustrating the another load sensor;
[0030] FIG. 12 is a schematic diagram view illustrating a first
example integration of the capacitance sensor and the load
sensor;
[0031] FIG. 13 is a schematic diagram view illustrating a second
example integration of the capacitance sensor and the load
sensor;
[0032] FIG. 14 is a schematic plan view illustrating positions of
senor cells of the load sensor;
[0033] FIG. 15A is a schematic plan view illustrating a first
contact area between an occupant seat and a child restraint system,
and FIG. 15B is a schematic plan view illustrating a second contact
area between the occupant seat and another child restraint
system;
[0034] FIG. 16A is a schematic plan view illustrating position
relationship between the first contact area and the sensor cells,
and FIG. 16B is a schematic plan view illustrating position
relationship between the second contact area and the sensor
cells;
[0035] FIG. 17 is a schematic plan view illustrating positions of
three senor cells of the load sensor;
[0036] FIG. 18 is a circuit diagram illustrating the load sensor
having the three sensor cells; and
[0037] FIG. 19A is a schematic plan view illustrating position
relationship between the first contact area and the three sensor
cells, and FIG. 19B is a schematic plan view illustrating position
relationship between the second contact area and the three sensor
cells.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0038] As shown in FIG. 1, an occupant detection system 10 includes
a detection electronic control unit (ECU) 11, a capacitance sensor
12, a load sensor 13, an airbag ECU 14a, an airbag 14b, an airbag
ON-light 15, and an airbag OFF-light 16. The detection ECU 11 and
the airbag ECU 14a may correspond to a controller.
[0039] The capacitance sensor 12 will be described with reference
to FIG. 2. An occupant seat 33 includes a seat bottom 34 and a seat
back 35. An occupant is seated on the seat bottom 34, and a back of
the occupant reclines on the seat back 35. A bottom frame 34a is
disposed in a lower part of the seat bottom 34, and is connected to
a vehicle chassis 32 to be grounded. A back frame 35a is disposed
in the seat back 35, and is connected to the vehicle chassis
32.
[0040] The capacitance sensor 12 includes a sensor part 31 disposed
in the seat bottom 34. The sensor part 31 is sandwiched between an
upper cover (not shown) and a cushion (not shown) of the seat
bottom 34, and is located to oppose to the bottom frame 34a through
an interval.
[0041] The sensor part 31 has a main electrode 31a, a sub-electrode
31b, and a guard electrode 31c. The main electrode 31a and the
sub-electrode 31b are located adjacent to the upper cover, and the
guard electrode 31c is located adjacent to the cushion.
[0042] The sub-electrode 31b is located adjacent to the main
electrode 31a, but is distanced from the main electrode 31a. The
guard electrode 31c is located to oppose to the main electrode 31a
through an interval, and is positioned between the main electrode
31a and the bottom frame 34a. The sensor part 31 and the detection
ECU 11 are connected through a connector wiring 36 such as a wire
harness.
[0043] An object to be detected by the capacitance sensor 12 has an
equivalent circuit shown in FIG. 3. For example, the capacitance
sensor 12 detects human body or seat wetness. As shown in FIG. 3,
the equivalent circuit has a resistor RMX and a capacitor CMX
connected to parallel with each other.
[0044] The resistor RMX represents a real part R corresponding to a
conductance, and the capacitor CMZ represents an imaginary part C
corresponding to a susceptance. Therefore, a capacitance of the
object is detected by detecting an impedance Z having the real part
R and the imaginary part C shown in FIG. 4.
[0045] When sine wave VSG shown in FIG. 5A is applied to the
object, potential difference is generated to a current-detecting
resistor (not shown) of the detection ECU 11 in accordance with the
impedance Z of the object.
[0046] In a case that the impedance Z has only the real part R, the
potential difference does not have a phase advance .theta. relative
to the sine wave VSG. When the potential difference is sampled by a
sampling timing shown in FIG. 5B, an output signal shown in FIG. 5D
is obtained.
[0047] FIG. 5D shows the real part R changed from current to
voltage, when the real part R is relatively large, and when the
imaginary part C is approximately zero. The sampling timing of FIG.
5B has the same phase as the sine wave VSG, and the output signal
shown in FIG. 5D is output based on only the real part R.
[0048] In a case that the impedance Z has only the imaginary part
C, the potential difference has a phase advance .theta. relative to
the sine wave VSG. When the potential difference is sampled by a
sampling timing shown in FIG. 5C, an output signal shown in FIG. 5E
is obtained.
[0049] FIG. 5E shows the imaginary part C changed from current to
voltage, when the real part R is approximately zero, and when the
imaginary part C is relatively large. The sampling timing of FIG.
5C has the phase advance of 90.degree. relative to the sine wave
VSG, and the output signal shown in FIG. 5E is output based on only
the imaginary part C.
[0050] Because an actual object always has both of the real part R
and the imaginary part C, the impedance Z having the phase .theta.
is measured. Determination to be described below is performed based
on the impedance Z.
[0051] Thus, the detection ECU 11 measures capacitance based on an
electric line of force generated from the sensor part 31. That is,
current flowing through the current-detecting resistor is converted
to voltage based on a supply signal from the sine wave VSG.
[0052] When the detection ECU 11 selects the main electrode 31a and
the guard electrode 31c, the determination is performed by the
capacitance between the main electrode 31a and a ground GND. When
the detection ECU 11 selects the sub-electrode 31b and the guard
electrode 31c, the determination is performed by the capacitance
between the sub-electrode 31b and the ground GND.
[0053] The detection ECU 11 measures the impedance Z of the object
by using the capacitance sensor 12, and determines a state of the
occupant seat 33 based on the impedance Z among a vacancy state,
CRS-mounted state, or adult-seated state.
[0054] As shown in FIG. 6, in a capacitance determination based on
the capacitance sensor 12, the adult-seated state is determined to
be ON. Further, the CRS-mounted state is determined to be OFF, and
the vacancy state is determined to be VACANT.
[0055] The load sensor 13 will be described with reference to FIG.
7.
[0056] The load sensor 13 includes a sensor switch 41 and a
resistor 42. The switch 41 may be a known membrane switch, for
example. The switch and the resistor 42 are connected in series
between the detection ECU 11 and the ground. The switch 41 is
arranged on a back side of the upper cover of the seat bottom 34.
When an occupant is seated on the seat bottom 34, or when the CRS
is mounted on the seat bottom 34, the switch 41 is ON by a load of
the occupant or CRS.
[0057] When the occupant nor the CRS are not on the seat bottom 34,
that is when nothing is on the seat bottom 34, the switch 41 is
OFF. When the occupant or the CRS is on the seat bottom 34, the
switch 41 is ON. A signal of ON or OFF is output into the detection
ECU 11. As shown in FIG. 6, in a load determination based on the
load sensor 13, an ON-signal is output when the switch 41 is ON,
and an OFF-signal is output when the switch 41 is OFF.
[0058] The detection ECU 11 performs a final determination based on
the capacitance determination and the load determination. The
airbag ECU 14a controls the ON-light 15 and the OFF-light 16 based
on the final determination.
[0059] When the capacitance determination is ON indicating the
adult-seated state, and when the load determination is ON or OFF,
the final determination is ON indicating the adult-seated state,
and the airbag ECU 14a turns on the ON-light 15.
[0060] When the capacitance determination is OFF indicating the
CRS-mounted state, and when the load determination is ON or OFF,
the final determination is OFF indicating the CRS-mounted state,
and the airbag ECU 14a turns on the OFF-light 16.
[0061] When the capacitance determination is VACANT indicating the
vacancy state, and when the load determination is ON, the final
determination is OFF indicating the CRS-mounted state, and the
airbag ECU 14a turns on the OFF-light 16.
[0062] In contrast, when the capacitance determination is VACANT
indicating the vacancy state, and when the load determination is
OFF, the final determination is VACANT indicating the vacancy
state, and the airbag ECU 14a turns off both of the ON-light 15 and
the OFF-light 16.
[0063] In a case that the CRS is mounted on the seat bottom 34,
when the capacitance is quite small, the capacitance sensor 12 may
erroneously determine the seat 33 to be vacant. However, in this
case, the load sensor 13 outputs the ON-signal, because a load of
the CRS is detected. As a result, the detection ECU 11 determines
the seat bottom 34 to have the CRS thereon, such that the final
determination is OFF indicating the CRS-mounted state. Thus, the
airbag ECU 14a turns on the OFF-light 16.
[0064] While the ON-light 15 is on, if the vehicle has a collision,
the airbag 14b is inflated by the airbag ECU 14a. While the
OFF-light 16 is on, even if the vehicle has a collision, the airbag
14b is not inflated. While both of the ON-light 15 and the
OFF-light 16 are off, even if the vehicle has a collision, the
airbag 14b is not inflated.
[0065] According to the embodiment, the occupant detection system
includes the capacitance sensor 12 to output current or voltage
based on a disturbance of a weak electric field generated between
an electrode disposed in the occupant seat 33 and a ground. The
disturbance is different among an occupant-seated state, a
CRS-mounted state, and a vacancy state.
[0066] Further, the occupant detection system includes the load
sensor 13 arranged in the occupant seat 33. When a predetermined
load is applied to the load sensor 13 through the occupant seat 33,
the load sensor 13 is in on state so as to output current or
voltage. When the predetermined load is not applied to the load
sensor 13, the load sensor 13 is in off state.
[0067] The occupant detection system includes the detection ECU 11
and the airbag ECU 14a so as to control the airbag ON-light 15
indicating an inflation allowable state of the airbag 14b, and the
airbag OFF-light 16 indicating an inflation prohibited state of the
airbag 14b.
[0068] When the capacitance sensor 12 outputs an occupant-seated
state signal, and when the load sensor 13 is in on state or off
state, the ON-light 15 is turned on. When the capacitance sensor 12
outputs an CRS-mounted state signal, and when the load sensor 13 is
in on state or off state, the OFF-light 16 is turned on. When the
capacitance sensor 12 outputs a vacancy state signal, and when the
load sensor 13 is in on state, the OFF-light 16 is turned on. When
the capacitance sensor 12 outputs the vacancy state signal, and
when the load sensor 13 is in off state, both of the ON-light 15
and the OFF-light 16 are turned off.
[0069] In a case that the CRS is mounted, on the occupant seat 33,
the capacitance sensor 12 erroneously may output the vacancy state
signal, because the capacitance is so small. However, in this case,
the load sensor 13 is in on state by detecting the load of the CRS.
Therefore, the detection ECU 11 determines the occupant seat 33 to
be in the CRS-mounted state, and the airbag ECU 14a turns on the
airbag OFF-light 16.
[0070] When the occupant seat 33 is vacant, the capacitance sensor
12 outputs the vacancy state signal, and the load sensor 13 is in
off state. Therefore, the detection ECU 11 determines the occupant
seat to be vacant, and the airbag ECU 14a turns off both of the
ON-light 15 and the OFF-light 16.
[0071] Thus, the vacancy state and the CRS-mounted state can be
accurately distinguished from each other. Therefore, when the seat
33 is vacant, both of the ON-light 15 and the OFF-light 16 are
turned off.
[0072] The load sensor 13 has a circuit shown in FIG. 7.
Alternatively, the load sensor 13 may be another load sensor 13'
having a circuit shown in FIG. 11A or FIG. 11B.
[0073] As shown in FIG. 8, the load sensor 13' includes a first
sensor cell 51, a second sensor, cell 52, a connector 53, and a
conductive part 54 electrically connecting the sensor cell 51, 52
and the connector 53. The sensor cell 51, 52 works as a conducting
switch to conduct when a load is applied to the sensor cell 51, 52
by an occupant or object. The sensor cells 51, 52 are connected by
the conductive part 54, and the connector 53 is connected to an end
of the conductive part 54 opposite from the first sensor cell 51.
The connector 53 is connected to the detection ECU 11.
[0074] As shown in FIG. 9, a cross-section of the load sensor 13'
is constructed by a first film 61, a second film 62, a first
electrode 63, a second electrode 64 and a spacer 65. A basic
construction is common between the sensor cell 51, 52 and the
conductive part 54, but a specific difference between the sensor
cell 51, 52 and the conductive part 54 will be described below.
[0075] The first film 61 is made of polyethylene naphthalate (PEN)
resin having a thin shape. The first film 61 defines an outer form
of the sensor cell 51, 52 and the conductive part 54, and has a
linear shape as a whole. Each of the end-located sensor cell 51 and
the center-located sensor cell 52 has an approximately circle shape
made of the first film 61. The conductive part 54 has a linear
shape, and a width of the linear shape is smaller than a diameter
of the circle shape. A base end of the first film 61 is connected
to the connector 53.
[0076] The second film 62 is made of the same material as the first
film 61, and has the same shape as the first film 61. The second
film 62 is located to oppose to the first film 61. A base end of
the second film 62 is connected to the connector 53, similarly to
the first film 61.
[0077] The first electrode 63 is arranged on an inner face of the
first film 61, as shown in FIG. 9, and has a silver layer 63a and a
carbon layer 63b. The silver layer 63a is bonded to the inner face
of the first film 61, and the carbon layer 63b covers a surface of
the silver layer 63a.
[0078] The second electrode 64 is arranged on an inner face of the
second film 62, as shown in FIG. 9, and has a silver layer 64a and
a carbon layer 64b. The silver layer 64a is bonded to the inner
face of the second film 62, and the carbon layer 64b covers a
surface of the silver layer 64a.
[0079] The carbon layer 64b of the second electrode 64 is distanced
from the first electrode 63. That is, the first electrode 63 and
the second electrode 64 are located to oppose to and be separated
from each other, in the sensor cell 51, 52.
[0080] The spacer 65 is disposed between the carbon layers 63b,
64b. An outer shape of the spacer 65 is the same as the film 61,
62. As shown in a broken line of FIG. 8, a hollow extending in a
longitudinal direction of the conductive part 54 is defined in a
center part of the spacer 65. A width of the hollow of the sensor
cell 51, 52 is larger than that of the conductive part 54. The
spacer 65 is made of polyethylene terephthalate (PET) resin having
a thin shape.
[0081] As shown in FIG. 9, a space is defined among the first
electrode 63, the second electrode 64, and the spacer 65. When load
is applied to the space in an up-and-down direction of FIG. 9, the
first film 61, the second film 62, the first electrode 63 and the
second electrode 64 have distorted deformations. Thus, the
electrodes 63, 64 are electrically connected, because the
electrodes 63, 64 contact with each other. That is, the sensor cell
51, 52 works as a conducting switch to electrically connect the
electrodes 63, 64, when a load is applied.
[0082] As shown in FIG. 10, the load sensor 13' is arranged in a
manner that the sensor cells 51, 52 are located symmetric with
respect to a center line of the seat 33. The load sensor 13' is
located between the cushion and the upper cover of the seat bottom
34 of the seat 33.
[0083] When the load sensor 13' has a circuit shown in FIG. 11A,
the end-located sensor cell 51 and the center-located sensor cell
52 are connected in parallel to the detection ECU 11 through the
connector 53. When at least one of the sensor cells 51, 52 has
conducting, the detection ECU 11 detects the load.
[0084] When the load sensor 13' has a circuit shown in FIG. 11B,
the end-located sensor cell 51 and the center-located sensor cell
52 are connected in series with the detection ECU 11. When both of
the sensor cells 51, 52 have conduction, the detection ECU 11
detects the load.
[0085] When the load sensor 13' detects the occupant-seated state
or the CRS-mounted state of the seat 33, a seatbelt state is
detected and output to the detection ECU 11. The detection ECU 11
lights or blinks a seatbelt warning (not shown), if the seatbelt is
not used for the occupant or the CRS.
[0086] The films 61, 62 of the load sensor 13' have liner shape.
When plural films 61, 62 are cut in a large base material,
patterning is performed in a state that the films 61, 62 are
arranged in parallel with each other. Thus, yield from the base
material can be better, because waste of the base material is
reduced. Therefore, the producible number of the films 61, 62 from
a single base material can be increased, such that cost of
producing the load sensor 13' can be reduced.
[0087] The load sensor 13' has the electrodes 63, 64 to contact
with each other when a load is applied. The electrodes 63, 64 are
arranged to oppose to and be separated from each other between the
films 61, 62. Thus, a construction of the load sensor 13' can be
simple.
[0088] When a sensor using a strain gauge is used as the load
sensor 13, detection accuracy of load can be improved. Thus, final
determination accuracy of the detection ECU 11 can be improved.
[0089] As shown in FIG. 12, the capacitance sensor 12 and the load
sensor 13, 13' are mounted to faces of a board-shaped urethane pad
71 opposite from each other. Thus, the capacitance sensor 12 and
the load sensor 13, 13' are integrated with each other as a single
sensor device 72. The sensor device 72 is connected to the
detection ECU 11. In this case, a size of the sensor device can be
small, and the sensor device can be easily mounted in the seat
33.
[0090] As shown in FIG. 13, the capacitance sensor 12 and the load
sensor 13, 13' are mounted to faces of a board-shaped urethane pad
71 opposite from each other. Thus, the capacitance sensor 12 and
the load sensor 13, 13' are integrated with each other as a single
sensor device 78. Further, the sensor device 78 is connected to the
detection ECU 11 through a connector 77. In this case, a size of
the sensor device can be small, and the sensor device can be easily
mounted in the seat 33.
[0091] As shown in FIG. 14, the sensor cells 51, 52 of the load
sensor 13' are located at predetermined positions of the seat
bottom 34. In this case, the load sensor 13' has an electric
circuit shown in FIG. 11A. When one of the sensor cells 51, 52 is
electrically conducted, the detection ECU 11 obtains detection
signal.
[0092] In US, for example, the mounting of the CRS to the seat
bottom 34 is defined in a law Appendix A of FMVSS208. Nineteen
kinds of CRS are defined in the law. Further, thirty-seven
configurations are defined in the law as for the mounting of the
CRS. In the thirty-seven configurations, the CRS is arranged in a
forward-looking direction or a backward-looking direction, or the
direction of the CRS is fixed to the forward-looking direction or
the backward-looking direction. A contact area between the CRS and
the seat bottom 34 is different in the thirty-seven configurations.
Not only a case in which only the CRS is mounted to the seat bottom
34, but also a case in which the one-year-old child is seated in
the CRS are defined for the mounting of the CRS.
[0093] A broken line of FIG. 15A shows a contact area 101 between
the seat bottom 34 and the CRS. A front part of the contact area
101 extends outward from an approximately center position in a
left-right direction so as to define an elongated band shape.
Further, the contact area 101 extends rearward from the front part
in a front-rear direction so as to define an elongated meandering
shape.
[0094] A broken line of FIG. 15B shows another contact area 102
between the seat bottom 34 and another CRS. The contact area 102
extends rearward from a front position so as to define an elongated
shape on left and right sides of the seat bottom 34.
[0095] In a case that shapes of the contact area 101, 102 are
different from each other, when the sensor cells 51, 52 have
positions shown in FIG. 16A, the CRS can be detected, because the
sensor cells 51, 52 are located inside of the contact area 101.
However, when the sensor cells 51, 52 have positions shown in FIG.
16B, the CRS cannot be detected, because the sensor cells 51, 52
are located outside of the contact area 102. About 70% of the
thirty-seven configurations have the contact area shown 101 in FIG.
16A.
[0096] When the sensor cells 51, 52 are positioned at the
predetermined positions in the contact area 101 of FIG. 16A, about
70% of the thirty-seven CRS-mounted configurations can be
detected.
[0097] As shown in FIG. 17, the load sensor 13' further includes
another sensor cell 56 other than the sensor cells 51, 52, and the
sensor cell 56 is disposed at a predetermined position of the seat
bottom 34. In this case, the load sensor 13' has an electric
circuit shown in FIG. 18. The sensor cells 51, 52, 56 are connected
parallel to the detection ECU 11. When at least one of the sensor
cells 51, 52, 56 is electrically conducted, the detection ECU 11
obtains detection signal.
[0098] As shown in FIGS. 19A and 19B, at least one of the sensor
cells 51, 52, 56 is located in the contact area 101, 102 on the
seat bottom 34, even when the shapes of the contact area 101, 102
are different between FIG. 19A and FIG. 19B. That is, the sensor
cells 51, 52, 56 are located at the predetermined positions so as
to detect the CRS relative to all of the thirty-seven CRS-mounted
configurations.
[0099] Thus, because the CRS-mounted state can be properly detected
for all of the thirty-seven configurations, the vacancy state and
the CRS-mounted state can be properly determined and distinguished
from each other. Therefore, both of the ON-light 15 and the
OFF-light 16 can be turned off in the vacancy state.
[0100] Such changes and modifications are to be understood as being
within the scope of the present invention as defined by the
appended claims.
* * * * *